RECENT ADVANCES IN IMMUNITY TO HUMAN SCHISTOSOMIASIS

For many years the epidemiological significance of immunity in human s chistosomiasis has been the subject of inconclusive debate. Recently, the results of studies from Brazil and Kenya, on Schistosoma mansoni a nd from Zimbabwe and The Gambia on S. haematobium have confirmed the i mportance of protective immunity. In communities in endemic areas the development of immunity to infection only occurs after many years of e xposure. In part this is due to the slow development of antibodies whi ch are protective but also to the earlier development of antibody isot ypes which lack protective capacity and which are capable of interferi ng with the functioning of protective antibodies. Protective antibodie s appear to be of the IgE class but some IgG subclasses may also be im portant. Initially, blocking antibodies were thought to be predominant ly IgM and IgG2 but IgG4 also seems to possess blocking activity. The early production of blocking antibodies and late production of protect ive antibodies may be indicative of cytokine induced immunoglobulin cl ass switching caused by the sequential involvement of different lympho kines.